DESCRIPTION: The purpose of this project is to define a set of genes whose expression is altered, over expression or suppression, early in treatment of an animal with a carcinogen. As a first set of experiments to measure changes in expression during carcinogen treatment, groups of B6C3F1 mice were treated with 7, 12-dimethyl benz [alpha] anthracene, furan, and trichloroethylene. After two weeks treatment, target tissues were obtained and mRNA extracted, radiolabeled probes prepared and hybridized to mouse Atlas(TM) arrays on membranes (Clontech). The expression patterns on the 588 sequences for the treated tissues were compared to those of RNA extracted from untreated control animals. Significant differences in expression between treated and control tissues were observed. In order to establish that these differences are the result of carcinogen treatment and not simply toxicity to the compounds used, pairs of isomers where one is carcinogenic and the other toxic will be used to treat animals. The changes in gene expression for the two compounds will be measured to determine the specific response to the carcinogen of the apri. This analysis will be performed at 14 and 90 days of treatment for at least two pairs of compounds. Analysis of changes in expression will be performed using mouse Atlas(TM) arrays (currently 1,176 sequences) on glass slides. Fluorescent probes will be prepared using two different labels and comparative analysis for two probes performed on the same slide. These analyses will be extended to tumors induced by the compounds used where tumors can be obtained. A database of gene expression changes will be established in phase II by testing the ability of a large number of known carcinogens to alter gene expression of both known genes (the Atlas(TM) arrays for example) and random ESTs. These results will establish expression patterns indicative of a carcinogen. PROPOSED COMMERCIAL APPLICATION: The product of this research will be a database containing the expression patterns of tissues from animals treated with carcinogens. The congruence of these patterns for different types of carcinogens will establish the genes required to manufacture a "carcinogencity array" to be used in the testing of new compounds. These arrays will be used to test new compounds for client companies first as additional data to accompany the chronic studies and subsequently as a stand alone assay.